title: Lack of cross-resistance to a novel succinate dehydrogenase inhibitor, fluopyram, in highly boscalid-resistant isolates of Corynespora cassiicola and Podosphaera xanthii.
abstract: BACKGROUND
  Recently in Japan, isolates resistant to boscalid, a succinate dehydrogenase inhibitor (SDHI), have been detected in Corynespora cassiicola (Burk. & Curt.) Wei and Podosphaera xanthii (Castaggne) Braun & Shishkoff, the pathogens causing Corynespora leaf spot and powdery mildew disease on cucumber, respectively. Resistant isolates of C. cassiicola are widely distributed and represent a serious problem in disease control at present. Novel SDHI fungicides, including fluopyram, are now under development.
  
  
  RESULTS
  The growth of very highly boscalid-resistant, highly resistant and sensitive isolates of C. cassiicola was strongly suppressed on fluopyram-amended YBA agar medium. Although boscalid and another SDHI, penthiopyrad, hardly controlled Corynespora leaf spot and powdery mildew on cucumber plants when very highly or highly boscalid-resistant isolates were employed for inoculation, fluopyram still exhibited excellent control efficacy against these resistant isolates as well as sensitive isolates of C. cassiicola and P. xanthii.
  
  
  CONCLUSIONS
  Differential sensitivity to boscalid, penthiopyrad and fluopyram, clearly found in these two important pathogens of cucumber, may indicate involvement of a slightly distinct site of action for fluopyram from the two other SDHIs. This finding may lead to the discovery of unique SDHIs in the future.
authors.affiliation: National Institute for Agro-Environmental Sciences, Tsukuba, Ibaraki, Japan. hideo@affrc.go.jp
authors.forename: Hideo
authors.initials: H
authors.lastname: Ishii
authors.forename: Takuya
authors.initials: T
authors.lastname: Miyamoto
authors.forename: Shingo
authors.initials: S
authors.lastname: Ushio
authors.forename: Makoto
authors.initials: M
authors.lastname: Kakishima
mesh_terms: D001203:Ascomycota / Q000187:drug effects* / Q000201:enzymology / Q000302:isolation & purification; D001549:Benzamides / Q000494:pharmacology*; D001713:Biphenyl Compounds / Q000494:pharmacology*; D018553:Cucumis sativus / Q000382:microbiology; D025141:Drug Resistance, Fungal; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005656:Fungal Proteins / Q000037:antagonists & inhibitors*; D005659:Fungicides, Industrial / Q000494:pharmacology*; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D010935:Plant Diseases / Q000382:microbiology*; D011725:Pyridines / Q000494:pharmacology*; D013385:Succinate Dehydrogenase / Q000037:antagonists & inhibitors*
chemical_list: D001549:Benzamides; D001713:Biphenyl Compounds; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D005659:Fungicides, Industrial; D011725:Pyridines; D009536:Niacinamide; C550088:2-chloro-N-(4-chlorobiphenyl-2-yl)nicotinamide; D013385:Succinate Dehydrogenase; C572868:N-(2-(3-chloro-5-(trifluoromethyl)-2-pyridyl)ethyl)-alpha,alpha,alpha-trifluoro-o-toluamide